Holographic display étendue expansion with a binary π-metasurface

Holographic displays trade field of view against eyebox size because a spatial light modulator provides a fixed étendue. We pair a commercial 4-bit piston-mode phase light modulator (PLM) with a pixel-registered binary metasurface designed for an achromatic π phase step. Grouping the PLM into s×s superpixels while retaining native mask sampling increases the modeled angular-support area by s² with one passive element. Scalar simulations and three-color experimental captures at 450, 520, and 660 nm show matched operation from one fixed mirror bias. A fixed-depth diffractive element leaks 7.0% and 11.9% of the power into an unexpanded ghost at 450 and 660 nm, which the metasurface's full-wave-simulated zero order holds to 0.3% and 2.7%.